html{
    font-family: "microsoft yahei, arial, helvetica, sans-serif";
    font-size: 16px;
    background-image: url("../assets/image/400.jpeg");
    background-size: cover; /* 覆盖整个页面 */
    background-position: center; /* 居中显示 */
    background-attachment: fixed; /* 固定背景，不随滚动条滚动 */
  }